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LMR16006 Schottky Diode failure

Carl D Schrubbe
Prodigy 130 points
Other Parts Discussed in Thread: LMR16006

We have a new design - 24vdc input max - 5vdc out - customer had under test - un-plugged unit -reconnected - unit failed;

Unit is fully potted - dissolved potting compound with MEK - 

unfortunately, potting compound expanded when dissolved and damaged choke  - 

Schottky diodes was damaged - looked to be cracked open.

Removed LMR16006 and placed on good board - it was ok.

D3 Schottky diode is 1 amp 100v

Any Ideas?

Thanks

Schottky diode

  • 0
    TI__Genius 15810 points

    Hello,

    Could you also send the layout image? Maybe there was a bad spike during plug that presented at the SW node. Is this failure on multiple boards? If the IC is fine then it could be a bad diode.

    Regards,

    Akshay

  • 0 in reply to Akshay Mehta
    Prodigy 130 points

    Hi

    Here is foil  - top of board is ground plane - power enters from connector "V"

    H1 and H2 are solid connected- and the entire unit is potted.

    We have only had a single failure - unfortunately it was during a customer acceptance test.

    Thanks

    Carl

  • 0 in reply to Carl D Schrubbe
    TI__Genius 10115 points

    Hi Carl.

    Capacitor C3 and diode D3 grounds should be touching,

    That said I don't think the spikes should have been enough to damage a 100V diode.  I would put a scope probe on the cathode of D3 and observe the switching waveform.  Look at the overshoot above Vin.  Then add a short ( thru hole resistor lead) from C3 to D3 ground and see if the ringing improves.

    When you are testing the part.  How is it being turned on and off? Maybe something there can give us a clue.

    Regards,

    Marc

  • 0 in reply to Marc Davis-Marsh
    TI__Guru 66925 points

    Also:

    I would put C3 next to device, then rotate diode next to C3, then put the 2.2uF.

    Might need some tant or Al input cap to help prevent any ringing or spikes at input.